The present invention relates to the field of polyol finishing processes. More particularly, it relates to a polyol finishing process having reduced amounts of solid or liquid wastes.
Methods for preparing and finishing polyols are numerous in the art. Commonly a catalyst is used in the polyol preparation process, and such catalyst is typically a basic catalyst such as KOH or another alkali metal hydroxide. In this case it is desirable to remove the catalyst or neutralize it with an acid before using the polyol for a final purpose, since the basicity in the polyol may adversely affect the reaction or reactivity which is sought. Such is especially true when a polyol is to be used to prepare a polyurethane, related product, since the presence of unneutralized catalyst may result in over-catalysis of the reaction desired, e.g., a polyurethane-forming reaction. Weak acids and dilute acids can be used for the neutralization and the resultant salts left in the polyol in some cases, but the salts tend to act as catalysts when the polyol is used in certain reactions such as for polyurethane formation, and enhance the rate of reaction to an undesirable or unacceptable extent.
To counter the undesirable effects of leaving the resultant salts in the polyols, various means of their removal have been developed. For example, processes combining crystallization and filtration allow for removal of the salts. Other known means of removing salts include extraction, for example, washing, and adsorption using various adsorbants including, for example, ion exchange media.
However, the means of removal have some significant disadvantages. One disadvantage is that they require one, or more, separate removal steps following the neutralization, which involves in many cases additional time, equipment expense, solvent expense and the like. The waste salt generally must be disposed of in some manner, necessitating additional cost and, in some cases, causing environmental concerns. Finally, the basic catalyst, e.g., KOH, which has been converted to the salt (which may be a solid or dissolved salt), cannot generally be recycled without expensive techniques.
Accordingly, it would be desirable in the art to have a means of "finishing" a polyol that would preferably reduce processing steps, reduce waste products that must be removed, and allow easier recycle of at least a portion of the basic catalyst.